Using various techniques of RNA/DNA hybridization, this project will continue defining the highest level of gene regulation which is altered in the various stages of carcinogenesis and tumor progression. The early effects of radiation on RNA transport to the cytoplasm will be determined, to compare this form of cancer initiation with the alteration of RNA transport which is characteristic of chemical carcinogens on their target tissues. Radionuclide-induced tumors will also be assayed for this defect, as will additional spontaneous tumors. If the RNA transport defect appears to be an essential changes during carcinogenesis, an attempt will be made to design an assay for cancer initiating factors based on the very early appearance of this alteration. Studies will continue on the relationship between loss of transcription of repetitive DNA, loss of transcription of nonrepetitive DNA, and loss of hormone dependence during tumor progression, and factors affecting the rate of these changes. BIBLIOGRAPHIC REFERENCES: Shearer, Ruth W. (1976) Differences and similarities in RNA regulation between tumors induced by chemicals and by DNA and RNA viruses. (Symposium on Molecular Biology and Biochemistry of the Cancer Cell, Moscow, June 1975). In press, Bulletin of the Academy of Medical Sciences, U.S.S.R. Shearer, Ruth W. (1976) Altered control of transcription during tumor progression. Presented at the Third International Symposium on Detection and Prevention of Cancer, New York, April 1976. In press, in book, Marcel Dekker, Inc., New York.